3.73 rear end gears - The 1947 - Present Chevrolet & GMC Truck Message Board Network

asolde · 06-29-2014, 07:34 AM

I finally took the 72 Blue Blazer out on the road yesterday. I took it down the freeway and I don't think I wanted to go much faster than 55mph. I don't have a tach so I don't know what rpm I was running the old engine at but it felt like I was pushing it. Tires are 31x10.5x15. The transmission seems to be ok except it leaks through the adaptor I keep an eye on the fluid level. Is this normal? Thanks Alex

87Skier · 06-29-2014, 12:18 PM

Is what normal? Feeling like you are pushing it or that it leaks through the adapter? If you mean it feels like you are pushing it, it is probably because the engine turning around 2300 rpm at 55 mph.

asolde · 06-29-2014, 12:26 PM

Quote:

Originally Posted by 87Skier

Is what normal? Feeling like you are pushing it or that it leaks through the adapter? If you mean it feels like you are pushing it, it is probably because the engine turning around 2300 rpm at 55 mph.

Feeling like I am pushing at 55 mph. The high rpm of the engine is what I am concerned about. The adaptor leak I know what I got to do there and I will wait until it cools down a little to take on that job.

pound41 · 06-29-2014, 03:46 PM

yes I have 2 blazers with 373 and thats the way they do. my other with 3:08 cruises.

**DeadheadNM** · 06-29-2014, 09:14 PM

With 31" tires that's what I recall as regards my now gone 72 K10 - my K5 also has 3.73's but 33" tires (and TH350) - can post rpm at 55 mph if it helps. Pete

asolde · 07-01-2014, 06:21 PM

Quote:

Originally Posted by DeadheadNM

With 31" tires that's what I recall as regards my now gone 72 K10 - my K5 also has 3.73's but 33" tires (and TH350) - can post rpm at 55 mph if it helps. Pete

Maybe I should put my 31" on my 69 with the 3.07 gear and put a bigger tire on my 72 with the 3.73. How big of tire could put on a stock height Blazer?

**DeadheadNM** · 07-01-2014, 06:43 PM

Quote:

Originally Posted by asolde

Maybe I should put my 31" on my 69 with the 3.07 gear and put a bigger tire on my 72 with the 3.73. How big of tire could put on a stock height Blazer?

That's a good idea Alex. 33" should fit with a stock lift and fill out the wheel well nice. There are online RPM calculators that could show you the rpm drop going to a 33" or so tire...

06-29-2014, 07:34 AM	#1
asolde Registered User Join Date: Apr 2012 Location: Henderson Nevada Posts: 804	3.73 rear end gears I finally took the 72 Blue Blazer out on the road yesterday. I took it down the freeway and I don't think I wanted to go much faster than 55mph. I don't have a tach so I don't know what rpm I was running the old engine at but it felt like I was pushing it. Tires are 31x10.5x15. The transmission seems to be ok except it leaks through the adaptor I keep an eye on the fluid level. Is this normal? Thanks Alex __________________ 1972 cheverolet K5 CST Blazer 350/auto/AC/PS/PB/Aux Batt From Medford, Oregon

06-29-2014, 12:18 PM	#2
87Skier Registered User Join Date: Mar 2014 Location: Corvallis, OR Posts: 715	Re: 3.73 rear end gears Is what normal? Feeling like you are pushing it or that it leaks through the adapter? If you mean it feels like you are pushing it, it is probably because the engine turning around 2300 rpm at 55 mph. __________________ 1972 GMC Jimmy Custom 4.8L (L20)/6L90E/NP205 1989 Chevy Suburban V2500 350/Turbo 400/4.11 gears 1996 Chevy Suburban K1500 350/4L60E

06-29-2014, 03:46 PM	#4
pound41 Registered User Join Date: Dec 2002 Location: Northern Virginia Posts: 1,268	Re: 3.73 rear end gears yes I have 2 blazers with 373 and thats the way they do. my other with 3:08 cruises.

06-29-2014, 09:14 PM	#5
DeadheadNM Carpe manana Join Date: Dec 2010 Location: Eau Claire, WI Posts: 12,447	Re: 3.73 rear end gears With 31" tires that's what I recall as regards my now gone 72 K10 - my K5 also has 3.73's but 33" tires (and TH350) - can post rpm at 55 mph if it helps. Pete __________________ 1972 K5 CST Highlander Blazer: http://67-72chevytrucks.com/vboard/s...d.php?t=708547 1972 K20 Cheyenne Super: http://67-72chevytrucks.com/vboard/s...d.php?t=528308 Members met: ORANGBLAZ, 2003 silverado, MikeCofield, BB72CHEVKT, Duncan&Son, Sameyrasmea72, THENEWMEXICAN, HotRod C/10, brianthelion02, Sport/Truck, ryanroo, michael bustamante, Dirt's72, Already Gone, WestButteTruck, 57taskforce, Moreyel, painterljp, AASmedic, SoCoC10, Lumaestas, carbuff382, Chevyland



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